The present invention relates to a method of reading recorded information from an information storage medium such as a compact disk (CD), a laser vision disk (LVD), or the like in which desired information is recorded in spiral tracks.
Generally, information is recorded in an optical disk at a predetermined velocity (constant linear velocity or constant angular velocity). The recorded information is typically in the form of pits successively arranged in the spiral tracks on a time-series basis. The recorded information is read from the optical disk by an optical pickup, which generates a reproduced signal in a real-time manner.
In order to accurately read the recorded information, the tracks must be scanned or traced accurately. It has been customary to employ a tracking servo control system such as a three-beam method, a push-pull method, or the like for correcting tracking errors.
Therefore, the conventional read-out devices employ tracking servo control for proper tracking. However, when a read-out device is subjected to a strong external shock, the beam spot applied from the optical pickup to the optical disk may move out of the tracking servo control range. This is a phenomenon known as a track jump. In the event of a track jump, the beam spot is shifted to a track other than the track which is to be traced by the beam spot, with the result that some recorded information is skipped in the reproduced sound. The track jump is caused in CD and LVD players.
The track jump occurs due to external forces applied to optical disk players, and should be distinguished from an intentional or forced track jump in trick play and search modes.